U.S. patent application number 13/515154 was filed with the patent office on 2012-11-22 for process for manufacturing an acoustic panel for an aircraft nacelle.
This patent application is currently assigned to AIRCELLE. Invention is credited to Emmanuel Drevon.
Application Number | 20120291937 13/515154 |
Document ID | / |
Family ID | 42732306 |
Filed Date | 2012-11-22 |
United States Patent
Application |
20120291937 |
Kind Code |
A1 |
Drevon; Emmanuel |
November 22, 2012 |
PROCESS FOR MANUFACTURING AN ACOUSTIC PANEL FOR AN AIRCRAFT
NACELLE
Abstract
Process for manufacturing an acoustic panel for an aircraft
nacelle. The invention relates to a process for manufacturing an
acoustic panel (1) for a nacelle of an aircraft, said panel (1)
comprising a metallic acoustic absorption structure (7) and an
acoustic skin (3) having a multitude of acoustic openings (5), said
process comprising: - a step A in which a layer (21) is formed that
contains a polymerizable insulating material around the acoustic
openings (5) of the acoustic skin (3), said insulating material
being configured to protect the acoustic absorption structure (7)
from corrosion; - a step B in which the layer (21) thus obtained is
solidified by polymerization.
Inventors: |
Drevon; Emmanuel;
(Anglesqueville L'Esneval, FR) |
Assignee: |
AIRCELLE
Gonfreville l'Orcher
FR
|
Family ID: |
42732306 |
Appl. No.: |
13/515154 |
Filed: |
December 6, 2010 |
PCT Filed: |
December 6, 2010 |
PCT NO: |
PCT/FR2010/052619 |
371 Date: |
June 11, 2012 |
Current U.S.
Class: |
156/60 ;
427/207.1; 427/271; 427/287 |
Current CPC
Class: |
B64D 2033/0286 20130101;
B64D 2033/0206 20130101; G10K 11/172 20130101; B64D 33/02 20130101;
Y10T 156/10 20150115; B32B 15/20 20130101; B32B 3/12 20130101; B32B
15/08 20130101 |
Class at
Publication: |
156/60 ; 427/287;
427/271; 427/207.1 |
International
Class: |
B05D 5/00 20060101
B05D005/00; B32B 37/12 20060101 B32B037/12; B05D 5/10 20060101
B05D005/10 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 11, 2009 |
FR |
09/05998 |
Claims
1. A process for manufacturing an acoustic panel for a nacelle of
an aircraft, said panel comprising a metallic acoustic absorption
structure and an acoustic skin having a multitude of acoustic
openings, said process comprising: a step A in which a layer is
formed that contains a polymerizable insulating material around the
acoustic openings of the acoustic skin, said insulating material
being configured to protect the acoustic absorption structure from
corrosion; a step B in which the layer thus obtained is solidified
by polymerization.
2. The method according to claim 1, wherein, during the step A, the
layer of insulating material deposited on the acoustic skin is
heated.
3. The method according to claim 1, wherein the heating temperature
is comprised between 50.degree. C. and 200.degree. C.
4. The method according to claim 1, wherein, in the step A, a
broken layer of insulating material is deposited by spraying said
insulating material on the acoustic skin so as to form a layer of
insulating material around the acoustic openings.
5. The method according to claim 1, wherein in the step A, the
layer of insulating material is formed around the acoustic openings
by first depositing a continuous layer of insulating material on
the entire surface of the acoustic skin, then freeing the acoustic
openings thus obstructed by heating and/or blowing through said
acoustic openings.
6. The method according to claim 1, wherein the polymerizable
insulating material comprising a thermosetting materials with a
base of at least one of epoxide, polyimide, or bismaleimide, and
thermoplastic materials.
7. The method according to claim 1, wherein, in the step B, the
polymerization is done at a temperature higher than or equal to the
ambient temperature and/or at a pressure greater than or equal to
the ambient pressure, in an autoclave or stove
8. The method according to claim 1, wherein before the step A, the
acoustic skin is solidified by heating at a temperature between
100.degree. C. and 250.degree. C. and under a pressure between 2
bars and 8 bars.
9. The method according to claim 1, wherein, during the step B, the
acoustic skin and the layer of insulating material formed on said
skin during the step are solidified substantially simultaneously by
polymerization.
10. The method according to claim 1, comprising a step in which a
layer of adhesive material is formed on the layer of insulating
material around the acoustic openings.
11. The method according to claim 10, wherein the layer of adhesive
material is deposited by spraying around the acoustic openings.
12. The method according to claim 10, wherein a continuous layer of
adhesive material is deposited on the layer of insulating material
and the material obstructing the acoustic openings is removed by
heating and/or blowing through said acoustic openings.
13. The method according to claim 12, wherein a layer of adhesive
material is deposited on a continuous layer of insulating
material.
14. The method according to claim 1, wherein in the step A, a layer
consisting of a first ply of insulating material topped by a second
ply of adhesive material is deposited, said first ply and second
ply being configured to be polymerized during the step B.
15. The method according to claim 10, wherein the polymerization
speed of the adhesive material is lower than that of the insulating
material.
16. The method according to claim 15, wherein the adhesive material
comprises a thermosetting material& with a base of at least one
of epoxide, polyimide, or bismaleimide, and thermosetting
materials.
17. The method according to claim 1, wherein the acoustic skin
comprises a plurality of stacked layers of flat composite tapes
each oriented by their longitudinal axis defining a direction, the
longitudinal axes of the tapes of a same layer being parallel to
one another, said tapes of the same layer being spaced apart from
one another so as to have acoustic openings in the acoustic
skin.
18. The method according to claim 1, comprising a step C in which
the acoustic structure is fastened on the acoustic assembly
obtained at the end of step B.
Description
TECHNICAL FIELD
[0001] The present invention relates to a process for manufacturing
an acoustic panel for an aircraft nacelle.
BACKGROUND
[0002] Aircraft turbojet engines create significant noise
pollution. There is a strong demand to reduce this pollution,
particularly given that the turbojet engines used are becoming more
and more powerful. The design of the nacelle surrounding a turbojet
engine contributes in large part to reducing this noise
pollution.
[0003] In order to further improve the acoustic performance of
aircrafts, nacelles are equipped with acoustic panels intended to
attenuate the noise created by the turbojet engines.
[0004] Acoustic panels are sandwich-type structures well known for
absorbing these noises. These panels usually comprise one or more
layers of a cellular core structure (commonly called "honeycomb"
structure). These layers are generally covered on their so-called
outer surface with an air-impermeable skin, called "solid," and on
the inner surface thereof, i.e. the surface in contact with the
flow of air and the sound excitation inside the engine, a
perforated air-permeable skin, called "acoustic."
[0005] The acoustic panel can also include several structural
layers trapping the noise called "sound absorption layers," between
which a multi-perforated skin called "septum" is located. The sound
absorption structure may be a cellular core structure containing a
multitude of honeycomb cells. The septum is generally adhered
between the noise-trapping structures by polymerization during the
assembly/adhesion phase of the panel.
[0006] The acoustic panel is assembled by positioning the different
skins and layers, which are then pasted on a mold having the
appropriate shape. The assembly is then cured in a furnace so as to
grip the layers and polymerize the adhesives.
[0007] Such panels make up acoustic resonators capable of
"trapping" the noise and therefore attenuating the sound emissions
toward the outside of the nacelle.
[0008] Typically, acoustic panels include an acoustic skin and a
solid skin made from composite materials.
[0009] Acoustic panels are known in which the acoustic skin is
already perforated before being assembled with the acoustic
absorption structure. Examples include acoustic skins such as those
described in application FR09/05605, the acoustic openings of which
are formed during the manufacture of said skin.
[0010] It is common to use a metal acoustic absorption structure in
this type of panel, in particular made from aluminum.
[0011] However, if the perforated acoustic skin made from a
carbon-type composite material is in contact with the metal
acoustic absorption structure, then a galvanic corrosion phenomenon
occurs in which the acoustic skin made from the carbon-type
composite acts as a cathode and the acoustic absorption structure
made from metal acts as an anode. This causes a deterioration of
the metal sound absorption structure and, as a result, of the
acoustic panel.
[0012] It is therefore necessary to protect this type of panel from
the galvanic corrosion phenomenon.
[0013] To that end, a continuous layer of fiberglass plies is
usually inserted between the acoustic skin and the sound absorption
structure. However, the acoustic openings of the acoustic skin
being obstructed by the glass layer, it is necessary to perform a
step for perforating said layer of glass, which is long and
expensive.
[0014] In the case of an openwork skin like that described in
application FR09/05605, the use of glass tapes appears relatively
implausible, because such tapes require draping a significant
number of glass plies to take into account the complex draping
configuration of the composite plies of the acoustic panel so as to
completely cover the latter part. Such a large number would also
have an impact on the mass of the acoustic panel.
BRIEF SUMMARY
[0015] One aim of the present invention is therefore to provide an
acoustic panel including an acoustic skin having, before placement
thereof, acoustic openings and a metal absorption structure, said
panel being protected from the galvanic corrosion phenomenon.
[0016] To that end, according to a first aspect, the invention
relates to a process for manufacturing an acoustic panel for a
nacelle of an aircraft, said panel comprising a metallic acoustic
absorption structure and an acoustic skin having a multitude of
acoustic openings,
[0017] said process comprising: [0018] a step A in which a layer is
formed that contains a polymerizable insulating material around the
acoustic openings of the acoustic skin, said insulating material
being configured to protect the acoustic absorption structure from
corrosion; [0019] a step B in which the layer thus obtained is
solidified by polymerization.
[0020] The panel obtained using the process according to the
invention therefore includes an acoustic skin comprising, before
the placement thereof, acoustic openings that are not obstructed
during production of the acoustic panel. Said skin is not in
contact with the metal acoustic absorption structure, but rather
with the layer of polymerizable insulating material, which protects
the acoustic absorption structure from corrosion without the
placement of said insulating material causing any obstruction of
the acoustic openings.
[0021] Advantageously, the process according to the invention makes
it possible to provide an acoustic panel without a step for
perforating the acoustic skin.
[0022] The invention thus makes it possible to simply provide
protection against galvanic corrosion by means of the polymerizable
insulating material inserted between the acoustic skin and the
acoustic absorption structure without making the mass of the
acoustic panel heavier, or increasing the number of steps to
manufacture said panel.
[0023] According to other features of the invention, the panel
according to the invention comprises one or more of the following
optional features, considered alone or according to all possible
combinations: [0024] during the step A, the layer of insulating
material deposited on the acoustic skin is heated; [0025] the
heating temperature is comprised between 50.degree. C. and
200.degree. C.; [0026] in the step A, a broken layer of insulating
material is deposited by spraying said insulating material on the
acoustic skin so as to form a layer of insulating material around
the acoustic openings; [0027] in the step A, the layer of
insulating material is formed around the acoustic openings by first
depositing a continuous layer of insulating material on the entire
surface of the acoustic skin, then freeing the acoustic openings
thus obstructed by heating and/or blowing through said acoustic
openings; [0028] the polymerizable insulating material is chosen
from among thermosetting materials with a base of epoxide,
polyimide, or bismaleimide, and thermoplastic materials; [0029] in
the step B, the polymerization is done at a temperature higher than
or equal to the ambient temperature and/or at a pressure greater
than or equal to the ambient pressure, in an autoclave or stove;
[0030] before the step A, the acoustic skin is solidified by
heating at a temperature between 100.degree. C. and 250.degree. C.
and under a pressure between 2 bars and 8 bars; [0031] during the
step B, the acoustic skin and the layer of insulating material
formed on said skin during the step (A) are solidified
substantially simultaneously by polymerization; [0032] a step in
which the layer of adhesive material is formed on the layer of
insulating material around the acoustic openings; [0033] the layer
of adhesive material is deposited by spraying around the acoustic
openings; [0034] a continuous layer of adhesive material is
deposited on the layer of insulating material and the material
obstructing the acoustic openings is removed by heating and/or
blowing through said acoustic openings; [0035] a layer of adhesive
material is deposited on a continuous layer of insulating material;
[0036] in the step A, a layer consisting of a first ply of
insulating material topped by a second ply of adhesive material is
deposited, said first ply and second ply being configured to be
polymerized during the step B; [0037] the polymerization speed of
the adhesive material is lower than that of the insulating
material; [0038] the adhesive material is chosen from among
thermosetting materials with a base of epoxide, polyimide, or
bismaleimide, and thermosetting materials; [0039] the acoustic skin
comprises a plurality of stacked layers of flat composite tapes
each oriented by their longitudinal axis defining a direction, the
longitudinal axes of the tapes of a same layer being parallel to
one another, said tapes of the same layer being spaced apart from
one another so as to have acoustic openings in the acoustic skin;
[0040] the process according to the invention comprises a step C in
which the acoustic structure is fastened on the acoustic assembly
obtained at the end of step B.
BRIEF DESCRIPTION OF THE DRAWINGS
[0041] The invention will be better understood upon reading the
following non-limiting description, done in reference to the
appended figures.
[0042] FIG. 1 is a diagrammatic transverse cross-section of a panel
obtained in the context of the present invention;
[0043] FIG. 2 is a diagrammatic transverse cross-section of an
acoustic skin already including acoustic openings and a layer of a
polymerizable insulating material in an embodiment of the step A of
the process according to the invention;
[0044] FIG. 3 is a diagrammatic transverse cross-section of the
layer of polymerizable insulating material mounted on the acoustic
skin at the end of the step A;
[0045] FIG. 4 is a diagrammatic transverse cross-section of the
acoustic skin fastened to the layer of insulating material of FIG.
3 at the end of an embodiment of the step B of the process
according to the invention;
[0046] FIG. 5 is a diagrammatic transverse cross-section of the
acoustic skin fastened to the layer of insulating material of FIG.
4 including a layer of adhesive material;
[0047] FIG. 6 is a diagrammatic transverse cross-section of the
embodiment of FIG. 5 at the end of cross-linking of the layer of
adhesive material;
[0048] FIG. 7 is a diagrammatic transverse cross-section of an
embodiment of part of an acoustic panel obtained at the end of the
process according to the invention according to the embodiments of
FIGS. 1 to 6;
[0049] FIGS. 8 to 10 are diagrammatic transverse cross-sections of
an alternative of the embodiments of FIGS. 3 to 6;
[0050] FIGS. 11 to 13 are diagrammatic transverse cross-sections of
another alternative of the embodiments of FIGS. 3 to 6.
DETAILED DESCRIPTION
[0051] The process according to the invention is intended to
manufacture an acoustic panel 1 for a nacelle of an aircraft (not
shown) comprising an acoustic skin 3 having acoustic openings 5,
said skin 3 being fastened to a metal acoustic absorption structure
7, which in turn is fastened to a solid skin 9.
[0052] The acoustic skin 3 used in the process according to the
invention is an acoustic skin having acoustic openings 5 before the
placement of said skin 3 on the acoustic absorption structure 7 in
the acoustic panel 1.
[0053] In this way, the acoustic skin 3 may have all types of
acoustic openings 5. The acoustic openings 5 may assume any shape,
as indicated above. Furthermore, the acoustic openings 5 may have a
diameter comprised between 0.5 mm and 3.0 mm.
[0054] In particular, the acoustic skin may be of the type
comprising a plurality of stacked layers of flat composite tapes
each oriented by their longitudinal axis defining a direction, the
longitudinal axes of the tapes of the same layer being parallel to
one another, said tapes of said same layer being spaced apart from
one another so as to have acoustic openings 5 in the acoustic skin
3, like the acoustic skins described in application FR09/05605.
[0055] In this way, the resin-impregnated fiber tapes are not
attached edge to edge or by overlapping, but have spaces between
them. In other words, the tapes of a same layer are not in contact
with one another. The layers are alternated so as to obtain
acoustic openings 5 in which the noise is capable of
penetrating.
[0056] The acoustic absorption structure 7 can, for example, be a
cellular core structure (see FIG. 1). The latter comprises a
plurality of walls 11 forming the cells 13, which are configured to
trap the noise.
[0057] The acoustic absorption structure 7 is made from a metal
material, such as aluminum.
[0058] The solid skin 9 is typically made by superimposing a
multitude of composite plies, in particular made up of
resin-impregnated carbon fiber fabrics, in particular of the
epoxide, polyimide or bismaleimide type.
[0059] Contrary to the acoustic skin 3, the solid skin 9 does not
comprise acoustic openings 5.
[0060] The process according to the invention includes: [0061] a
step A in which a layer 21 is formed containing a polymerizable
insulating material around acoustic openings 5 of the acoustic
skin, said insulating material being configured to protect the
acoustic absorption structure 7 from corrosion, while ensuring a
physical separation between the acoustic skin 3 and the acoustic
absorption structure 7; [0062] a step B in which the layer 21 thus
obtained is solidified by polymerization.
[0063] The process according to the invention therefore makes it
possible to use an acoustic skin 3 having acoustic openings 5
before the placement and fastening thereof in the acoustic panel
1.
[0064] In particular, the process according to the invention makes
it possible to provide an acoustic skin 1 without comprising a step
for perforating the acoustic skin 3, since the acoustic openings 5
thereof are not obstructed during the manufacture of said panel
1.
[0065] The invention then makes it possible to simply provide
protection against galvanic corrosion of the acoustic absorption
structure 7 by means of a polymerizable insulating material without
making the mass of the acoustic panel 1 heavier, or increasing the
number of steps in the production of said panel 1.
[0066] Typically, the layer of insulating material 21 has a
thickness comprised between 0.04 mm and 0.32 mm.
[0067] Typically, the polymerizable insulating material is a
material chosen from among thermosetting materials with a base of
epoxide, polyimide or bismaleimide, and thermoplastic
materials.
[0068] According to one embodiment, during the step A, the layer of
insulating material 21 deposited on the acoustic skin 3 is heated.
Heating this layer 21 makes it possible to start a sufficient
pre-polymerization to impart good cohesion to said layer, or even
also softening. In this way, the assembly formed by the acoustic
skin 5 topped by the layer of insulating material 21 is easier to
handle.
[0069] Typically, the heating temperature is between 50.degree. C.
and 200.degree. C. It is also possible for the insulating material
to be able to pre-polymerize, in other words to begin
polymerization, at ambient temperature.
[0070] According to one embodiment, in the step A, a broken layer
of insulating material 21 is deposited by spraying said insulating
material on the acoustic skin 3 so as to form a layer of insulating
material 21 around the acoustic openings 5. As a result, the layer
of insulating material 21 is formed around the acoustic openings 5
in a single step. In fact, the sprayed material attaches on the
material of the acoustic skin 3, and therefore around the acoustic
openings 5.
[0071] According to the embodiment of the process of the invention
illustrated in FIGS. 2 to 7, in a step A, the layer of insulating
material 21 is formed around the acoustic openings 5 by first
depositing a continuous layer of insulating material 21 on the
entire surface of the acoustic skin 3, then freeing the acoustic
openings 7 thus obstructed by heating and/or blowing through said
acoustic openings 7.
[0072] The layer of insulating material 21 is advantageously
deposited on the surface 23 of the acoustic skin 3 intended to be
fastened on the acoustic absorption structure 7.
[0073] It is possible for only heating or only blowing to be
necessary to form the acoustic openings 25 by removing the material
that was obstructing said openings.
[0074] In fact, the heating and/or blowing makes it possible to
create piercings in the material of the layer of isolating material
21 that obstruct the acoustic openings 5. The material is then
pressed on the edges of the acoustic openings 5. As a result, the
layer of insulating material 21 is formed around each acoustic
opening 5 without obstructing it.
[0075] The heating temperature can be between 50.degree. C. and
200.degree. C.
[0076] The blowing can be done using a nozzle moved manually or
automatically.
[0077] The continuous layer of insulating material 21 can be
deposited manually or automatically, for example using rollers.
[0078] The acoustic skin 3 used in this embodiment can be
solidified by polymerizing it before adding the layer of insulating
material 21, i.e. before the step A, which makes it possible to
apply the layer of insulating material 21 more easily. The
polymerization typically comprises of heating said skin 3 to a
temperature between 100.degree. C. and 250.degree. C. under a
pressure comprised between 2 bars and 8 bars
[0079] According to one embodiment not shown, the acoustic skin 3
is not polymerized before the step A, i.e. before the deposition of
the layer of insulating material 21, but rather during this step B
with the layer of insulating material 21 obtained at the end of the
step A. Thus, during the step B, the acoustic skin 3 and the layer
of insulating material 21 can be polymerized substantially
simultaneously. Advantageously, the number of steps of the
inventive process is thereby limited.
[0080] As illustrated in FIG. 3, during the step A, the layer of
insulating material 21 obstructs the acoustic openings 5 of the
acoustic skin.
[0081] At the end of the step A, the layer of insulating material
21 is deposited only on the material of the acoustic skin 3 and no
longer obstructs the acoustic openings 5. In other words, the layer
of insulating material 21 has acoustic openings 25 with a
substantially equal diameter, or a diameter that may even be larger
than that of the acoustic openings 5 of the acoustic skin. In this
way, the diameter of the acoustic openings 25 of said layer is
comprised between 0.5 mm and 3.0 mm.
[0082] During the step B, the layer of insulating material 21 is
solidified secured on said skin 3, and possibly the acoustic skin
3, by polymerization. The polymerization then consists of heating
to a temperature between 100.degree. C. and 250.degree. C. under a
pressure between 2 bars and 8 bars.
[0083] The process can then include an additional step C in which
the acoustic structure 7 is fastened on the acoustic assembly
obtained at the end of the step B. To that end, it is possible to
apply a layer of adhesive material on the layer of insulating
material 21 or on the acoustic absorption structure 7.
[0084] The adhesive material must make it possible to fasten the
layer of insulating material 21 by adhering it on the metal
absorption structure 7. Said adhesive material can be chosen from
among thermosetting materials with a base of epoxide, polyimide or
bismaleimide, and thermosetting materials.
[0085] The process according to the invention can comprise a step
in which a layer of adhesive material is formed on the layer of
insulating material 21 around the acoustic openings 25; 35 in order
to preserve the latter.
[0086] Typically, the layer of adhesive material 31 has a thickness
between 0.04 mm and 0.32 mm.
[0087] The process according to the invention may include a step in
which a layer of adhesive material 31 is deposited on the layer of
insulating material 21. Said layer of insulating material 21 may or
may not already be polymerized following the step B.
[0088] According to one embodiment, the layer of adhesive material
may be deposited by spraying around the acoustic openings 5,
25.
[0089] As illustrated in FIG. 5, a continuous layer of adhesive
material 31 may be deposited on the layer of insulating material
21. The layer of adhesive material 31 then obstructs the acoustic
openings 5 and 25.
[0090] In order to free said openings 5 and 25, it is possible to
heat and/or blow through the acoustic openings 5. The heating
temperature may be between 50.degree. C. and 200.degree. C.
[0091] Thus, as illustrated in FIG. 6, the layer of adhesive
material 31 has acoustic openings 35 in the extension of the
acoustic openings 5 and 25. The diameter of said acoustic openings
35 is typically substantially equal to or larger than the diameter
of the acoustic openings 5 and 25, in particular between 0.5 mm and
3.0 mm.
[0092] As illustrated in FIG. 7, the acoustic absorption structure
7 is placed on the layer of adhesive material 31. The assembly can
then be heated to a temperature between 100.degree. C. and
250.degree. C. at a pressure between 2 bars and 4 bars so as to
polymerize the layer of adhesive material to fasten the layer of
adhesive material 31 by adhesion on the acoustic absorption
structure 7. Thus, in the case of a cellular core structure, the
layer of adhesive material 31 forms a meniscus at the end of the
walls 11 of the cells in contact with said layer 31 without
obstructing said cells 13.
[0093] According to one alternative illustrated in FIGS. 8 and 9, a
layer of adhesive material 31 separate from the layer of insulating
material 21 is applied on the latter. The layer of adhesive
material 31 and the layer of insulating material 31 do not have
acoustic openings 35 and both obstruct the acoustic openings 5 of
the acoustic skin.
[0094] The acoustic openings 25, 35 are then formed in a single
step in the layers of insulating material 21 and adhesive material
31, in particular by heating and/or blowing, as indicated
above.
[0095] In the step B, the assembly formed by the layer of
insulating material 21 and the layer of adhesive material 31 is
polymerized (see FIG. 10).
[0096] As a result, the layer of insulating material 21 and the
layer of adhesive material 31 are deposited only on the material of
the acoustic skin 3 and therefore no longer obstruct the acoustic
openings 5.
[0097] The adhesive material can advantageously be slower to
polymerize than the insulating material. In other words, the
insulating material may have a higher polymerization speed than the
polymerization speed of the adhesive material, such that the
adhesive material solidifies during adhesion of the acoustic
absorption structure 7 and not before that assembly step. In fact,
if the adhesive material is in too advanced a stage of
polymerization, the fastening of the acoustic absorption structure
7 on the layer of adhesive material 31 creates periodic depositions
of glue that are detrimental to the gluing, and therefore the
adhesion of the acoustic panel 1.
[0098] The adhesive material may be chosen from among thermosetting
materials with a base of epoxide, polyimide or bismaleimide, and
thermosetting materials. The acoustic structure 7 can then be
placed and glued on the layer of adhesive material 31 as indicated
above, the gluing being able to be done under heating at a
temperature between 100.degree. C. and 250.degree. C. and under
pressure between 2 bars and 4 bars.
[0099] In an alternative illustrated in FIGS. 11 and 10, in the
step A, a single layer 41 may be deposited made up of a first ply
42 of insulating material and a second ply 43 of adhesive material
configured to be polymerized during the step B, said second ply 43
topping the first ply 42.
[0100] At the end of the step A, the layer 41 no longer obstructs
the acoustic openings 5. As a result, the number of steps of the
process according to the invention is further reduced. As before,
the adhesive material may be slower to polymerize than the
insulating material.
[0101] During the step B, the polymerization of the insulating
material may be done by heating or at ambient temperature by
allowing sufficient rest time. In the event heating is necessary,
the temperature is between 50.degree. C. and 200.degree. C.
[0102] In the step B, the polymerization may be done at a
temperature higher than or equal to the ambient temperature and/or
a pressure greater than or equal to the ambient pressure, in an
autoclave or a stove.
[0103] More specifically, the polymerization may be done at ambient
temperature or pressure.
[0104] The polymerization may be done in an autoclave at a
temperature and pressure substantially higher than the ambient
temperature and pressure.
[0105] The polymerization may be done in a stove at a temperature
substantially higher than the ambient temperature and ambient
pressure.
[0106] The embodiments described may of course be considered alone
or combined with one another without going beyond the scope of the
invention. To that end, for example, it is possible to spray the
layer of insulating material on the acoustic skin and, at the same
time or later, to spray the adhesive material or deposit the layer
of adhesive material in film form. It is also possible, after
depositing the layer of insulating material in film form, to spray
the adhesive material.
* * * * *